Disk drives are often used in electronic devices to record data onto or to reproduce data from a recording media, which can include one or more disks having recording surfaces. If the disk drive is subjected to a non-operational mechanical shock, such as when an electronic device is dropped, a disk inside the disk drive can deflect. Such disk deflection may be limited by contact between the disk and other components of the disk drive, such as the disk drive cover, ramp or base. Such contact may cause damage to the disk and result in a loss of data recorded on the disk.
In particular, non-operational mechanical shock may cause plastic deformation of a disk inside a disk drive when the disk contacts a non-uniform surface of the disk drive base. This problem is particularly a concern with aluminum disks, which have been used in the disk drive industry to replace more expensive glass disks. Furthermore, this problem is exacerbated in two respects when multiple disks are used in a disk drive. First, the extra weight of an additional disk increases the force with which a bottom disk impacts the base. Second, an additional disk may decrease the clearance available between the bottom disk and the base.
Electronic device manufacturer's specifications for mechanical shock robustness for disk drives are becoming more stringent, especially for disk drives used in mobile electronic devices. To meet such stringent specifications, a disk drive needs to survive more severe mechanical shocks. More severe mechanical shocks are more likely to cause impact between a disk and a base of the disk drive, despite a nominal clearance between the two. Moreover, the nominal clearance may not be practically increased to the extent necessary to prevent such impacts because of dimensional constraints of the disk drive or operational considerations.